ECD T90 Instruction Manual
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Contents
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Page 43 Model T80Press Yes/NO Remove the Sensor from Solution and dry the front end, Air = 0.00 μSTo perform zero CAL press CAL 1, to skip zero cal press CAL 2, only if a zero cal was previously done on the sensorPress AUTO then CAL 1 STABILIZING, 0.00 μS, 1.17 V, 0.00 μS corrected, Accept Cal?Press YES CAL 1 Value 0.00 μS, Continue to CAL2? Move sensor to 1.00 mS solutionPress YES STABILIZING, 1.00 mS, 98X.X mV, 1.000 μS corrected, Accept Cal?Press YES OFFSET: 0.00 ppm, 174.4 mV, SLOPE: 984 (data written to Log)Press OK Calibration completePress HOME Hold is ONPress HOLD Turn off HoldPress EXIT Main Display4.7.2 STANDARDIZEWith the sensor in the process solution, take a grab sample from the process and determine the conductivityusing a qualified laboratory conductivity meter.Action PromptDouble Press any Button MENU HOME, Hold is OFFPress HOLD Hold freezes 4-20 mA Output and locks Alarm Relays during CalibrationPress CAL Is this a new Sensor? (Yes, erases CAL Log in INFO, NO adds CAL to existing Log)Press NO With the sensor in the process solutionPress STAND Enter the laboratory determined conductivity valuePress ▲ ▼ NEXT xxx.xx μS/mS (use arrows and NEXT to enter process value)Press OK xxx.xx μS/mS, xxx.x mV, Accept Value?Press YES OFFSET: 0.00 μS 1.0 mV, SLOPE: xx.xx mV/ppm (this data written to Log)Press OK Back to Cal MenuPress HOME Hold is ON (Press HOLD to turn off Hold)Press HOLD Turn off HoldPress EXIT Main Display4.8 TDS CONDUCTIVITY SENSORSThe Total Dissolved Solids measurement (TDS) on the Model T80 transmitter is made with an S80 conductivitysensor and a correlation factor. (Conductivity in μS x correlation factor = ppm)Conductivity is a measurement of a solution’s electrolytic conductivity, 1/ohms. The type of dissolved ions in thesolution is irrelevant to the measurement. TDS is a measurement of concentration, ppm (mg/L). Since differentsalts contribute different amounts of conductivity to a solution, TDS measurements are only valid betweensolutions of the same chemical makeup. As an example, 1000 ppm of TDS in natural waters has a conductivityaround 1400 μS (correlation factor 0.6712), 1000 ppm of KCl has a conductivity around 2000 μS (correlationfactor 0.5000) and 1000 ppm of NaOH has a conductivity around 6000 μS (correlation factor 0.1667). All threesolutions have a TDS of 1000 ppm but the conductivities are 1400 μS, 2000 μS and 6000 μS. A TDS measurementis only valid for a solution with the same chemical make up as the solution used for calibration.Calibration is accomplished in two steps; Step 1 Conductivity AUTO Calibration of the sensor (see section 4.7.1above) and then Step 2 correlation of conductivity to the TDS. The second step can be done by entering thecorrelation factor into the CONFIG →SENSOR→ TDS menu or by standardizing the sensor in a solution of knownTDS in the CAL→STAND menu by entering the TDS value. Since the correlation of conductivity to concentration isnot linear it is best to calibrate the sensor near the measured value. |
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